An interesting article (linked below) from Al Jazeera which acknowledges the immense cost in planting hundreds of millions of trees to capture carbon. Thankfully research (and experience in Brazil) shows that by assisting nature (in specific ways) to do “her thing”, we can reduce the amount of physical planting humans have to do. The article highlights large areas where assisted regeneration could work. This would allow humankind to focus planting on areas of greatest need.
It makes sense. In the temperate Irish climate we are aware that abandoned farm land will quickly turn to what we call “scrub” (a mixture of the pioneer species). This is helped by the centuries old system of land division which left field sizes relatively small – half acre to four acre fields are not uncommon. And around each field? Mature hedgerows with viable seed sources! The article (link below) is referring specifically to “assisted” regeneration which is more strategic than what I describe happening here in Ireland. That said the carbon storage potential as well as the biodiversity benefit of letting land rewild is great. A few other thoughts…
1) For assisted natural regeneration to work, the trees (that we hope to assist) will have to reach sexual maturity before the process can really ramp up. This period until sexual maturity varies hugely by species and therefore it may slow initial carbon capture. Of course, if the seed source trees are already mature (like the hedgerows in the Irish example) then it becomes much quicker for the next generation of saplings to get established. Equally if the mature trees aren’t the species we want (e.g. perhaps non native trees that support little biodiversity) we may prefer to remove them and start from scratch. So in other words an acre of typical plantation forestry can have ten or even twenty years growth under its belt before an area of “assisted” regeneration is starting to seed out the next generation!
2) The article mentions the financial cost of large scale tree planting. There is also a huge carbon cost of industrial tree planting. Consider the energy inherent in seed collection, creating conditions for optimum growth in large scale tree nurseries, perhaps using fungicides or pesticides to prevent disease, the watering and maintenance of seedlings / saplings before transport to the “green field” to plant. In the Irish context heavy diesel powered machinery is employed to create optimum ground conditions for planting. Here it can involve JCB diggers creating mound drains. After the trees are planted maintenance begins. It can involve weedkiller applications to suppress competing vegetation and if the solid conditions aren’t optimum fertilisers are often added.
Anyway take a look at the link below and see what you think!
Last year, the journal Science published a study that made a bold – and elegantly simple – claim: To mitigate climate change, plant a trillion new trees. Authored by a team of scientists from various research institutions in Europe and the Food and Agriculture Organization of the United Nations, the study attracted considerable mainstream media coverage. Soon after, tree-planting initiatives […]